136 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Overall Description
— The A4 inverter converts dc voltage to the ac voltage required by the
display.
— A backlight (a bulb powered by the A4 Inverter) lights the display so that
information is visible.
— The A18 CPU generates data, which is routed to the LCD through the
A3 Power Switch assembly.
— To extend the life of the LCD, an available sleep mode turns the LCD off
after a defined inactive period (no key presses or program commands) and
turns it back on with any key press.
RF Output Connector
On 20 GHz instruments, the RF output connector is an APC 3.5 male or
Type–N (Option 1ED). On models with output frequencies above 20 GHz and
<50 GHz, the RF output connector is a 2.4 mm male. On models with output
frequencies above 50 GHz, the RF output connector is a 1.85 mm male
connector. Option 1EM moves all front panel connectors to the rear panel.
Rear Panel
The rear panel contains the power line module, LAN, GPIB, RS–232, and A20
Source Module Interface (SMI), scalar interface, and BNC connectors used for
sweep interface. BNC and SMB connectors may be present on the rear panel
but not operational if the option associated with that connector is not installed.
Frequency Generation
The YIG oscillator generates frequencies from 3.2 to 10 GHz.
Output
Frequency
Oscillator
Frequency
Path Notes
< 250 MHz 3.2 to 10 GHz
Lowband path,
and part of
highband path
A6 Frac–N signal is mixed with a 1 GHz signal on the A8 output assembly;
the difference is used to generate the lower frequencies.
250 MHz
to
3.2 GHz
4 to 8 GHz Oscillator output is divided by 2/4/8/16 on the A6 Frac–N assembly.
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